Metric Bolt Torque Chart

Size (mm)	Recommended Maximum Tightening Torque (Nm)
	Grade 8.8	Grade 9.8	Grade 10.9	Grade 12.9
M5	7.0	7.8	10.0	11.7
M6	11.8	13.3	17.0	19.9
M8	28.8	32.3	41.3	48.3
M10	57.3	64.1	81.8	95.7
M12	99.8	112	143	167
M16	248	277	354	413
M20	500		690	809
M24	865		1195	1395
M30	1719		2377	2774

Sample Torque Question

Question: What is the recommended tightening torque for an M10 bolt Grade 12.9, and how does it compare to Grade 8.8?

Bolt Size	Bolt Grade	Torque (Nm)
M10	Grade 8.8	57.3
M10	Grade 12.9	95.7

Answer: Grade 12.9 bolts have a higher tensile strength and can be tightened to 95.7 Nm compared to 57.3 Nm for Grade 8.8 bolts. This represents approximately 67% higher torque capacity for the same bolt size.

Washer Selection Guide

Proper washer selection is critical for bolt grade compatibility and load distribution. Different hardness values (HV) must be matched with bolt grades to prevent galling and ensure secure fastening.

Important Note: Grade 12.9 bolts require washers with higher hardness (HV) values to prevent washer deformation under high tensile loads. Using soft washers (Grade 8.8 specification washers) with Grade 12.9 bolts can result in surface damage and stress concentration.

Grade 8.8 Bolt Washers

Bolt Size	HV Range	Washer Type (ISO 7090)	Normative
M5-M10	160-200 HV	Steel Washer	ISO 7090 / DIN 125
M12-M16	180-220 HV	Steel Washer	ISO 7090 / DIN 125
M20-M30	200-240 HV	Steel Washer	ISO 7090 / DIN 125

Grade 12.9 Bolt Washers

Bolt Size	HV Range	Washer Type	Normative
M5-M10	280-320 HV	Hardened Steel Washer	ISO 7090 / DIN 125 (Grade 10.9+)
M12-M16	300-340 HV	Hardened Steel Washer	ISO 7090 / DIN 125 (Grade 10.9+)
M20-M30	320-360 HV	Hardened Steel Washer	ISO 7090 / DIN 125 (Grade 10.9+)